1. Field of the Invention
This invention relates to twisting tumbler locks and particularly to a method and apparatus for decoding twisting tumbler locks. The invention further relates to improvements in twisting tumbler locks for defeating the decoding methods and apparatus.
2. The Prior Art
Twisting tumbler locks typified by the cylinder lock described in U.S. Pat. No. 3,499,302, granted to R. C. Spain et al. on Mar. 10, 1970, for Cylinder Lock have had an enormous impact on the lock industry. Such locks, which rely not only on the vertical positioning of the tumblers so that their upper surfaces are in the shear plane of the cylinder but further rely on the angular position of the tumblers in order to free a reciprocable movable side bar which serves as an supplementary locking means. Because there are two variables encountered with respect to each tumbler in order to properly position that tumbler into the "unlock" position, locks of this type have been to date highly pick resistant.
Locks of the type described in the aforementioned Spain et al U.S. Pat. No. 3,499,302 are sold in the United States under the registered mark MEDECO and are manufactured by the Medeco Security Locks Inc. of Salem, Virginia. These Medeco locks, while embodying the invention of said aforementioned U.S. Pat. No. 3,499,302 somewhat differ structually from the structures described and claimed in said patent.
The Medeco locks, which are now widely employed have posed serious problems to locksmiths, especially on what is generally called a "lockout". In a lockout, the authorized occupant of premises protected by a Medeco lock has misplaced his key and is unable to gain normal entry to the premises. When a locksmith is summoned, the locksmith is usually unable to employ the normal picking techniques used on many other types of cylinder locks in order to open the lock to gain entry. Thus, locksmiths often find themselves in a position where they must destroy the lock or the door supporting the lock in order to gain entry for the occupant. Such crude techniques are repugnant to locksmiths. This has tended to discourage their recommending Medeco locks for use by their customers.